Adiabatic thermal pulse compensating pressure transducer and method

ABSTRACT

Disclosed is a pressure transducer including a body made of a material having a first coefficient of thermal expansion, a fluidic inlet and a fluidic cavity enclosed by the body in fluidic communication with the fluidic inlet. The pressure transducer further includes a strain gauge including a resistive element in operable contact with the body. At least a portion of the resistive element made of a material having a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion of the body. Disclosed further is a pressure transducer including a filler body located in a fluidic cavity of the pressure transducer configured to reduce adiabatic thermal effects on a transducer body. Disclosed are systems and methods incorporating the pressure transducers described herein.

RELATED APPLICATIONS

This application is a non-provisional patent application claimingpriority to U.S. Provisional Patent Application No. 62/675,849, filedMay 24, 2018, entitled “Pressure Transducer, System and Method,” whichis incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to pressure transducers. Moreparticularly, the invention relates to pressure transducers configuredto reduce thermal effects, liquid chromatography systems incorporatingpressure transducers, and methods of reducing thermal effects onpressure transducers.

BACKGROUND

A typical strain gage pressure transducer includes a full Wheatstonebridge foil strain gage mounted directly above a pressurized cavityhaving a suitable web thickness to allow for measurable deflection ofintermediate housing material located between the pressurized cavity andthe strain gage. The strain gage will typically have two active grids tomeasure deflection, and two less reactive grids to complete theWheatstone bridge. To provide an accurate reading, a strain gage musttypically be situated in an iso-thermal condition.

However, during periods of rapid compression and decompression,adiabatic heating and cooling of the medium within the pressurizedcavity often imparts a thermal disturbance to the housing and onto thestrain gage. This thermal disturbance may prevent the pressuretransducer from accurately measuring pressure until the thermaldisturbance has settled and the four transducer grids have returned toan iso-thermal state. There could be a significant delay in waiting forthe grids of the strain gage to return to an iso-thermal state. Thisdelay can be problematic and particularly undesirable in industries,such as high performance liquid chromatography (HPLC), where accuratereadings are necessary very quickly after rapid compression anddecompression occurs of solvent found in a pressurized cavity. Forexample, chromatographic solvent pumps operating with pressures largerthan 5,000 psi require accurate pressure readings immediately afterlarge pressure changes.

Thus, a strain gage pressure transducer configured to reduce thermaleffects, and methods of reducing thermal effects on a strain gagepressure transducer, would be well received in the art.

SUMMARY

In one aspect, the invention features a pressure transducer thatincludes a body made of a material having a first coefficient of thermalexpansion; a fluidic inlet; a fluidic cavity enclosed by the body influidic communication with the fluidic inlet; and a strain gaugeincluding a resistive element in operable contact with the body, atleast a portion of the resistive element made of a material having asecond coefficient of thermal expansion that is different from the firstcoefficient of thermal expansion of the body.

Additionally or alternatively, the resistive element further includes: afirst resistor in operable contact with the body; a second resistor inoperable contact with the body; a third resistor in operable contactwith the body; and a fourth resistor in operable contact with the body.

Additionally or alternatively, the first, second, third, and fourthresistors are operably connected to form a Wheatstone bridge, and thefirst and second resistors are active grids and the third and fourthresistors are balance grids.

Additionally or alternatively, the first, second, third, and fourthresistors are each made of the material having the second coefficient ofthermal expansion.

Additionally or alternatively, a difference in the first coefficient ofthermal expansion and the second coefficient of thermal expansion isconfigured to reduce settling time after an adiabatic thermal pulserelative to a second pressure transducer having the same properties asthe pressure transducer other than the second pressure transducer havingwell-matched coefficient of thermal expansions.

Additionally or alternatively, the second coefficient of thermalexpansion is greater than the first coefficient of thermal expansion.

Additionally or alternatively, the difference in the first coefficientof thermal expansion and the second coefficient of thermal expansion isconfigured to compensate for an adiabatic thermal pulse.

Additionally or alternatively, the difference in the first coefficientof thermal expansion and the second coefficient of thermal expansion islarge enough that an output voltage disturbance during the adiabaticthermal pulse becomes positive.

Additionally or alternatively, the active grids are positioned proximatethe fluidic cavity and wherein the balance grids are positioned distalto the fluidic cavity relative to the active grids.

Additionally or alternatively, the balance grids are positioned in linewith the active grids and wherein the balance grids are orthogonallyoriented relative to the active grids.

Additionally or alternatively, the first and second resistors are madeof the material having the second coefficient of thermal expansions andwherein the third and the fourth resistors are made of the materialhaving a third coefficient of thermal expansion that is different thanboth the first coefficient of thermal expansion and the secondcoefficient of thermal expansion.

Additionally or alternatively, the first resistor is directly connectedin series to a first active grid of the strain gauge, the secondresistors is directly connected in series to a second active grid of thestrain gauge, the third resistor is directly connected in series to afirst balance grid of the strain gauge, and the fourth resistor isdirectly connected in series to a second balance grid of the straingauge.

Additionally or alternatively, the first resistor is connected inparallel to a first active grid of the strain gauge, the secondresistors is connected in parallel to a second active grid of the straingauge, the third resistor is connected in parallel to a first balancegrid of the strain gauge, and the fourth resistor is connected inparallel to a second balance grid of the strain gauge.

In another aspect, the invention features a method of detecting pressurethat includes providing a first pressure transducer having a body and aresistive element attached to the body; mismatching a first coefficientof thermal expansion of the body to a second coefficient of thermalexpansion of the resistive element; and detecting pressure of a fluidsystem with the first pressure transducer.

Additionally or alternatively, the detecting pressure further comprisesdetecting pressure with the first pressure transducer during anadiabatic thermal pulse.

Additionally or alternatively, the method includes reducing settlingtime after the adiabatic thermal pulse relative to a second pressuretransducer having the same properties as the first pressure transducerother than the second pressure transducer having well-matchedcoefficient of thermal expansions.

Additionally or alternatively, the second coefficient of thermalexpansion is greater than the first coefficient of thermal expansion.

Additionally or alternatively, the method includes outputting a positiveoutput voltage during an adiabatic thermal pulse.

Additionally or alternatively, the method includes compensating, withthe mismatched first and second coefficient thermal expansions, for anadiabatic thermal pulse.

In another aspect, the invention features a liquid chromatography systemthat comprises: a solvent delivery system; a sample delivery system influidic communication with solvent delivery system; a liquidchromatography column located downstream from the solvent deliverysystem and the sample delivery system; a detector located downstreamfrom the liquid chromatography column; and a pressure transducerconfigured to detect a fluid pressure at a location in the liquidchromatography system, the pressure transducer comprising: a body madeof a material having a first coefficient of thermal expansion; a fluidicinlet; a fluidic cavity enclosed by the body in fluidic communicationwith the fluidic inlet; and a strain gauge including a resistive elementin operable contact with the body, at least a portion of the resistiveelement made of a material having a second coefficient of thermalexpansion that is different from the first coefficient of thermalexpansion of the body.

In another aspect, a pressure transducer comprises: a transducer bodyhaving a fluidic inlet, and a fluidic cavity in fluidic communicationwith the fluidic inlet and enclosed by the transducer body; a straingauge attached to the transducer body; and a filler body located in thefluidic cavity configured to reduce adiabatic thermal effects on thetransducer body.

Additionally or alternatively, the filler body reduces the crosssectional area of the fluidic cavity to a reduced cross sectional areathat is greater than or equal to an inlet cross sectional area at thefluidic inlet.

Additionally or alternatively, the filler body comprises the samematerial as the transducer body.

Additionally or alternatively, the filler body comprises a material thatis different from a material of the transducer body.

Additionally or alternatively, the pressure transducer is a flow throughpressure transducer.

Additionally or alternatively, the filler body is a cylindrical bodyhaving a diameter less than a diameter of the fluidic cavity and locatedin the fluidic cavity distal to the strain gauge.

Additionally or alternatively, the filler body is a tubular body havinga diameter less than a diameter of the fluidic cavity and located in themiddle of the fluidic cavity.

Additionally or alternatively, the filler body extends a substantiallength of the fluidic cavity.

Additionally or alternatively, the pressure transducer is a dead-endpressure transducer.

Additionally or alternatively, the pressure transducer is a diaphragmpressure transducer.

Additionally or alternatively, the filler body does not contact asensing region of an inner surface of the fluidic cavity, the sensingregion located directly below the strain gauge within the filler cavity.

In another aspect, a method comprises: providing a pressure transducerhaving a fluidic inlet, and a fluidic cavity in fluidic communicationwith the fluidic inlet and enclosed by the transducer body; attaching astrain gauge to the transducer body; integrating a filler body withinthe fluidic cavity; and reducing a volume of the fluidic cavity with thefiller body.

Additionally or alternatively, the method includes reducing adiabaticthermal effects on the transducer body with the filler body relative toa second pressure transducer having the same properties as the pressuretransducer other than the second pressure transducer fabricated withoutthe filler body.

Additionally or alternatively, the pressure transducer is a flow throughpressure transducer and wherein the filler body extends along a lengthof the fluidic cavity having a cavity cross sectional area, the methodfurther comprising: reducing the cavity cross sectional area to areduced cross sectional area along the length with the filler body,wherein the reduced cross sectional area is greater than or equal to aninlet cross sectional area at the fluidic inlet.

Additionally or alternatively, the integrating the filler body withinthe fluid cavity further comprises not contacting a sensing region of aninner surface of the fluidic cavity with the filler body, the sensingregion located directly below the strain gauge within the filler cavity.

In another aspect, a liquid chromatography system comprises: a solventdelivery system; a sample delivery system in fluidic communication withsolvent delivery system; a liquid chromatography column locateddownstream from the solvent delivery system and the sample deliverysystem; a detector located downstream from the liquid chromatographycolumn; and a pressure transducer configured to detect a fluid pressureat a location in the liquid chromatography system, the pressuretransducer comprising: a transducer body having a fluidic inlet, and afluidic cavity in fluidic communication with the fluidic inlet andenclosed by the transducer body; a strain gauge attached to thetransducer body; and a filler body located in the fluidic cavityconfigured to reduce adiabatic thermal effects on the transducer body.

Additionally or alternatively, the filler body reduces the crosssectional area of the fluidic cavity to a reduced cross sectional areathat is greater than or equal to an inlet cross sectional area at thefluidic inlet.

Additionally or alternatively, the filler body comprises the samematerial as the transducer body.

Additionally or alternatively, the filler body comprises a material thatis different from a material of the transducer body.

Additionally or alternatively, the pressure transducer is a flow throughpressure transducer.

Additionally or alternatively, the filler body is a cylindrical bodyhaving a diameter less than a diameter of the fluidic cavity and locatedin the fluidic cavity distal to the strain gauge.

Additionally or alternatively, the filler body is a tubular body havinga diameter less than a diameter of the fluidic cavity and located in themiddle of the fluidic cavity.

Additionally or alternatively, the filler body extends a substantiallength of the fluidic cavity.

Additionally or alternatively, the pressure transducer is a dead-endpressure transducer.

Additionally or alternatively, the pressure transducer is a diaphragmpressure transducer.

Additionally or alternatively, the filler body does not contact asensing region of an inner surface of the fluidic cavity, the sensingregion located directly below the strain gauge within the filler cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of this invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings, in which like reference numerals indicatelike elements and features in the various figures. For clarity, notevery element may be labeled in every figure. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A depicts a top view of an in-line pressure transducer inaccordance with one embodiment.

FIG. 1B depicts a side view of the pressure transducer of FIG. 1A inaccordance with one embodiment.

FIG. 1C depicts a cross sectional view of the pressure transducer ofFIGS. 1A and 1B taken at arrows A-A in accordance with one embodiment.

FIG. 2A depicts a strain gauge applicable to a surface of a pressuretransducer in accordance with one embodiment.

FIG. 2B depicts another strain gauge applicable to a surface of apressure transducer in accordance with one embodiment.

FIG. 2C depicts another strain gauge applicable to a surface of apressure transducer in accordance with one embodiment.

FIG. 3 depicts a surface of a pressure transducer having a strain gaugebeing subject to an adiabatic process in accordance with one embodiment.

FIG. 4 depicts a graph of a pressure transducer having a strain gaugewith a well matched coefficient of thermal expansion compared with thepressure transducer having a strain gauge with a mis-matched coefficientof thermal expansion in accordance with one embodiment.

FIG. 5 depicts an electrical schematic of a strain gauge of a pressuretransducer in accordance with one embodiment.

FIG. 6 depicts an electrical schematic of another strain gauge of apressure transducer in accordance with one embodiment.

FIG. 7A depicts a top view of an in-line pressure transducer inaccordance with one embodiment.

FIG. 7B depicts a side view of the pressure transducer of FIG. 7A inaccordance with one embodiment.

FIG. 7C depicts a cross sectional view of the pressure transducer ofFIGS. 7A and 1B taken at arrows B-B in accordance with one embodiment.

FIG. 8A depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 8B depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 8C depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 8D depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 8E depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 8F depicts a cross sectional view of a pressure transducer inaccordance with one embodiment.

FIG. 9A depicts a top view of a diaphragm pressure transducer inaccordance with one embodiment.

FIG. 9B depicts a cutaway view of the pressure transducer of FIG. 8Ataken at arrows C-C in accordance with one embodiment.

FIG. 10 depicts a graph of a pressure transducer having no filler bodycompared with the pressure transducer having a filler body in accordancewith one embodiment.

FIG. 11 depicts a schematic of a liquid chromatography system inaccordance with one embodiment.

DETAILED DESCRIPTION

Reference in the specification to “one embodiment” or “an embodiment”means that a particular, feature, structure or characteristic describedin connection with the embodiment is included in at least one embodimentof the teaching. References to a particular embodiment within thespecification do not necessarily all refer to the same embodiment.

The present teaching will now be described in more detail with referenceto exemplary embodiments thereof as shown in the accompanying drawings.While the present teaching is described in conjunction with variousembodiments and examples, it is not intended that the present teachingbe limited to such embodiments. On the contrary, the present teachingencompasses various alternatives, modifications and equivalents, as willbe appreciated by those of skill in the art. Those of ordinary skillhaving access to the teaching herein will recognize additionalimplementations, modifications and embodiments, as well as other fieldsof use, which are within the scope of the present disclosure asdescribed herein.

Referring to FIG. 1A, a top view of an in-line pressure transducer 100is shown. Similarly, FIG. 1B shows a side view of the pressuretransducer 100 and FIG. 1C shows a cross sectional view of the pressuretransducer 100 taken at arrows A-A. The pressure transducer 100 includesa body 102, a fluidic inlet 104, a fluidic outlet 106, and a fluidiccavity 108 extending between the fluidic inlet 104 and the fluidicoutlet 106. The fluidic cavity 108 is enclosed by the body 102. Whilethe embodiment shown includes both the fluidic inlet 104 and the fluidicoutlet 106, other embodiments contemplated include single endedtransducers including a single fluidic inlet that acts as both a fluidicinlet and a fluidic outlet. In this embodiment, the single fluidic inletmay be considered a fluidic interface port.

A strain gauge 110 is disposed on a surface 112 located on the outsideof the body 102. The surface 112 may be a flat surface as shown. Inother embodiments, the surface 112 may include one or more curvesthereon. The strain gauge 110 includes a Wheatstone bridge having afirst active grid 114 and a second active grid 116 located directlyabove the fluidic cavity 108 on the surface 112, along with a firstbalance grid 118 disposed above the fluidic cavity 108 on the surface112 and a second balance grid 120 disposed below the fluidic cavity 108on the surface 112.

The active grids 114, 116 and the balance grids 118, 120 may eachinclude one or more resistive elements 122 or resistors patterned onto athin carrier backing 124 attached directly to the surface 112. The thincarrier backing 124 may include an adhesive layer configured to attachthe grids 114, 116, 118, 120 to the surface 112. The resistive elements122 may each be thin metallic wires of foil having a particularelectrical resistance that changes with the strain on the resistiveelements 122. The resistive elements 122 may each be in operable contactwith the body 102 through the thin carrier backing 124. “Operablecontact” herein shall mean a state where the strain experienced by thebody 102 is transferred to the resistive elements 122 to change theelectrical resistance of the resistive elements 122. In other words, thethin carrier backing 124 may be located between the resistive elements122 and the body 102 despite the resistive elements 122 being operablycontacting the body 102 for the purposes of measuring strain.

The body 102 may be made of a material having a first coefficient ofthermal expansion. For example, the body 102 may be made from titanium,for example, and may include a coefficient of thermal expansion at oraround 10.8×10⁻⁶. In other embodiments, the body 102 may be made fromsteel or stainless steel having a coefficient of thermal expansionbetween around 17 and 18×10⁻⁶. In still other embodiments, the body 102may be made of any metallic material having a coefficient of thermalexpansion between 10-12×10⁻⁶. The body 102 may further be made of metalshaving coefficients of thermal expansion as high as 40×10⁻⁶ (for zinc,for example) and as low as 2×10⁻⁶ (for Invar, for example).

The resistive elements 122 may be made of a metallic material having acoefficient of thermal expansion that is different than the coefficientof thermal expansion of the body 102. For example, the resistiveelements 122 may be made of aluminum, having a coefficient of thermalexpansion at or around 21×10⁻⁶. In other embodiments, the resistiveelements 122 may be made of constantan and Karma allows that include,for example, nickel-chromium, having coefficients of thermal expansionbetween 13-14×10⁻⁶. In other embodiments, the resistive elements 122 maybe made of steel or stainless steel, having a coefficient of thermalexpansion between around 17-18×10⁻⁶. Whatever the embodiment, theresistive elements 122 may include a different coefficient of thermalexpansion than the body 102. In other words, the resistive elements 122may have a mismatched coefficient of thermal expansion relative to thebody 102.

In an exemplary embodiment, the body 102 may be made of titanium havinga coefficient of thermal expansion of 10.8×10⁻⁶ while the resistiveelements 122 may be matched to stainless steel or steel, having acoefficient of thermal expansion between 17 and 18×10⁻⁶. In thisexemplary embodiment, the coefficient of thermal expansion of theresistive elements 122 may be higher than that of the body 102. However,other embodiments are contemplated where the coefficient of thermalexpansion of the resistive elements 122 may be lower than that of thebody 102. Other examples are contemplated, such as both the body 102 andthe resistive elements 122 being made of different steels. In stillother embodiments, the body 102 may be made of steel and the resistiveelements may be matched to aluminum.

The level of mismatch between coefficients of thermal expansion of thebody 102 and the resistive elements 122 may be dependent on thethickness of body material between the fluid path 108 or path and thesurface 112 upon which the strain gauge 110 is located, or in otherwords the web thickness. In the case where the body 102 is made oftitanium, and the web thickness is 0.025 inches, a mismatch betweencoefficients of thermal expansion of the body 102 and the resistiveelements 122 may be approximately 10×10⁻⁶. In other words, the resistiveelements 122 may have coefficients of thermal expansion 10×10⁻⁶ higherthan the coefficient of thermal expansion of the body 102. This amounthas been found to correct the thermally induced transients ofchromatographic solvents, for example, in liquid chromatography systems.Various other degrees of mismatch may correct pressure transducershaving various web thicknesses and subject to various forms of adiabaticthermal events.

In other embodiments, only the active grids 114, 116 may have amismatched coefficient of thermal expansion relative to the body 102,but not the balance grids 118, 120. In other embodiments, the balancegrids 118, 120 may include a mismatched coefficient thermal expansionrelative to the body 102, but not the active grids 114, 116. In otherembodiments, all of the grids 114, 116, 118, 120 include a mismatchedcoefficient thermal expansion relative to the body 102. In still furtherembodiments, the body 102 may be made of a first material having a firstcoefficient of thermal expansion, the active grids 114, 116 may be madeof a second material having a second coefficient of thermal expansion,and the balance grids 118, 120 may be made of a third material having athird coefficient of thermal expansion.

The coefficient of thermal expansions of the grids 114, 116, 118, 120may be mismatched with the coefficient of thermal expansion of the body102 such that the difference between the coefficients of thermalexpansion may be large enough that an output voltage during an adiabaticthermal pulse becomes positive. In other embodiments, the differencebetween the coefficients of thermal expansion between the grids 114,116, 118, 120 and the body 102 may be configured to reduce settling timeafter an adiabatic thermal pulse relative to a second pressuretransducer having the same properties as the pressure transducer 100other than the second pressure transducer having well-matchedcoefficients of thermal expansion between the grids and the body of thesecond pressure transducer. For example, configured the differencebetween the coefficients of thermal expansion between the grids 114,116, 118, 120 and the body 102 may be configured to reduce settling timeby at least 50 percent relative to the second pressure transducer. Inother embodiments, the settling time may be reduced by at least 80 byusing mismatched coefficients of thermal expansion between the grids andbody compared to well-matched coefficients of thermal expansion. In thismanner, the difference in the coefficients of thermal expansion in thegrids 114, 116, 118, 120 and the body 102 may be configured tocompensate for an adiabatic pulse caused by, for example, fast increasesor decreases in pressure by actuating a valve or from a pump actuationcycle where fluid is rapidly compressed and decompressed in a liquidchromatography system (such as the system shown in FIG. 11 and describedherein below). In other embodiments, it is contemplated that thesettling time may intentionally be increased instead of beingintentionally reduced through the mismatched coefficients of thermalexpansion.

The fluidic cavity 108 may be considered a fluidic path or other fluidicbody configured to receive pressurized fluid. The strain gauge 110 maybe configured to detect the pressure in the fluidic cavity 108 or cavityby measuring the strain caused by the pressurized fluid on the body 102.The surface 112 may be a removed portion that is removed from the body102. In other embodiments, the surface 112 may be molded or otherwiseintegrated into the body 102. As shown in FIGS. 1B and 1C, the surface112 is located closer to the fluidic cavity 108 than the rest of theouter circumference of the body 102.

In the embodiment shown in FIGS. 1A-1C, the active grids 114, 116 arepositioned proximate the fluidic cavity 108, while the balance grids118, 120 are positioned distal to the fluidic cavity 108 relative to theactive grids 114, 116. In other words, the active grids 114, 116 arepositioned directly over the fluidic cavity 108 while the balance grids118, 120 are positioned above and below, respectively, the active grids114, 116. In other embodiments, shown in FIGS. 2A-2C, the active gridsand balance grids may be positioned in line with each other. In thisembodiment, the active grids and the balance grids may be orientedorthogonally relative to each other.

FIGS. 2A-2C show various embodiments of active and balance gridspositioned in other arrangements contemplated. The grids shown in theseembodiments may have a mismatched coefficient of thermal expansion tothe body upon which the grids are placed, like the embodiment describedhereinabove with respect to FIGS. 1A-1C. FIGS. 2A-2C show embodimentscontemplated are not limited by any particular position or orientationof the grids. In the embodiment shown in FIG. 2A, a surface 130 is shownhaving a first active grid 132, a second active grid 134, a firstbalance grid 136 and a second balance grid 138 of a strain gauge. Theactive grids 132, 134, and the balance grids 136, 138 may include thesame features as the active grids 114, 116 and the balance grids 118,120 shown in FIGS. 1A-1C. However, the grids 132, 134, 136, 138 may beoriented in a different arrangement than the grids 114, 116, 118, 120.It should be understood that the surface 130 may be a surface of anin-line pressure transducer such as the surface 112 of pressuretransducer 100. However, the surface 130 may be a longer surface thanthe surface 112 in order to accommodate the in-line grids 114, 116, 118,120 of the strain gauge. In the embodiment shown in FIG. 2A, the twoactive grids 132, 134 may be located between the two balance grids 136,138 in-line. As shown, the active grids 132, 134 may have a gridalignment with wire lengths that extend horizontally and connectingcurves extending vertically, while the balance grids 136, 138 may have agrid alignment with wire lengths that extends vertically and connectingcurves that extend horizontally. In this manner, the active grids 132,134 and the balance grids 136, 138 may be oriented orthogonally relativeto each other.

As shown in FIG. 2B, a surface 140 is shown having a first active grid142, a second active grid 144, a first balance grid 146 and a secondbalance grid 148 of a strain gauge. The active grids 142, 144, and thebalance grids 146, 148 may include the same features as the active grids114, 116 and the balance grids 118, 120 shown in FIGS. 1A-1C. Thesurface 140 may include the same features as the surface 130 shown inFIG. 2A. In the embodiment shown in FIG. 2B, the first active grid 142may be placed in a bottom position, followed the first balance grid 146,followed next by the second active grid 144 and finally by the secondbalance grid 148 on top, all oriented in-line. Like the embodiment inFIG. 2A, the active grids 142, 144 may be oriented orthogonally relativeto the balance grids 146, 148.

As shown in FIG. 2C, a surface 150 is shown having a first active grid152, a second active grid 154, a first balance grid 156 and a secondbalance grid 158 of a strain gauge. The active grids 152, 154, and thebalance grids 156, 158 may include the same features as the active grids114, 116 and the balance grids 118, 120 shown in FIGS. 1A-1C. Thesurface 150 may include the same features as the surface 130 shown inFIG. 2A. In the embodiment shown in FIG. 2C, the first active grid 152may be placed in a bottom position, followed the first balance grid 156,followed next by the second balance grid 158 and finally by the secondactive grid 154 on top, all oriented in-line. Like the embodiment inFIG. 2A, the active grids 152, 154 may be oriented orthogonally relativeto the balance grids 156, 158.

Referring now to FIG. 3, the surface 112 of the pressure transducer 100is shown. A darkened region 160 on the surface 112 in this Figurerepresents the strain of the surface due to an adiabatic event suchadiabatic heating or cooling caused by a rapid change in pressure withinthe thermal chamber or fluid path 108. Thus, the active grids 114, 116may be placed in a compressive state as a result of the body 102compressing from the adiabatic event or thermal wave. This compressionhas not impinged upon the balance grids 118, 120. Instead, the pullingto the center by the body 102 may actually create a state of expansionat the location of the body 102 located under the balance grids 118,120. As the thermal wave spreads outward (not shown), the wave amplitudemay dissipate and the contractive strain may be radially toward theouter edges on the left and right of the surface 112. As the thermalwave dissipates, the grids begin to return to their normal, isothermalstate. In the event that the coefficient of thermal expansion is greaterin the grids 114, 116, 118, 120 than the body 102, when the body 102contracts due to an adiabatic thermal event, the grids 114, 116, 118,120 would contract more. Since the grids 114, 116, 118, 120 are bondedto the surface 112 of the body 102 and thereby constrained with the thincarrier backing 124, the grids 114, 116, 118, 120 cannot contract asmuch as they would in a free non-bonded state. The result is an actualstrain measured by the strain gauge 110 increasing despite thecontraction naturally caused by the adiabatic event's thermal wave.Depending on the amount of the mismatch, it is even possible to have acontracting thermal event result in a positive output voltage, despitethe body 102 experiencing a contraction causing adiabatic event. With asmaller mismatch, the output voltage of the strain gauge 110 may be lessnegative and/or may have a smaller peak.

Referring now to FIG. 4, a graph 170 of the pressure transducer 100 isshown having the strain gauge 110 with a mismatched coefficient ofthermal expansion between the body 102 and the grids 114, 116, 118, 120compared to a pressure transducer having the same properties as thepressure transducer 100 except having well-matched coefficients ofthermal expansion between the body and the grids. The graph 170 plotspressure output of the strain gauges along the y-axis vs. settling timeon the x-axis. In particular, in the plot 172 of the mismatched pressuretransducer 100, the strain gauge pressure output returns to zero afteronly two seconds. In contrast, the plot 174 of the well-matched pressuretransducer returns to zero after ten seconds. This long settling timecan be undesirable in industries and applications where pressure must bedetected immediately and adiabatic thermal events are common.

Referring now to FIG. 5, an electrical schematic of a strain gauge 180of a pressure transducer such as the pressure transducer 100 inaccordance with one embodiment. The strain gauge 180 may be similar tothe strain gauge 110 and may include two active grids 181, 182 and twobalance grids 183, 184. However, unlike the strain gauge 110, the straingauge 180 may include additional thermal resistors 185, 186, 187, 188.Rather than the grids 181, 182, 183, 184 being the resistive elementhaving a mismatched coefficient of thermal expansion relative to thethermal expansion of the body, the additional thermal resistors 185,186, 187, 188 may be the resistive element having mismatchedcoefficients of thermal resistance relative to the body upon which theyare attached. In other embodiments, both the grids 181, 182, 183, 184and the additional thermal resistors 185, 186, 187, 188 may includemismatched coefficients of thermal resistance relative to the body. Theadditional thermal resistors 185, 186, 187, 188 may be low impedanceand/or low resistance circuit elements. The thermal resistors 185, 186,187, 188 may each be connected in series to respective active andbalance grids 181, 182, 183, 184, as shown. In the embodiment shown, thethermal resistors 185, 186 proximate the active grids 181, 182 may havethe same coefficient of thermal expansion as the thermal resistors 187,188 proximate the balance grids 183, 184 but may have differentresistances. In other embodiments, each of the thermal resistors 185,186, 187, 188 may have the same resistance and coefficients of thermalresistance. In other embodiments, each of the thermal resistors 185,186, 187, 188 may have the same resistance and different coefficients ofthermal resistance. In other embodiments, each of the thermal resistors185, 186, 187, 188 may have the different resistance and differentcoefficients of thermal resistance.

Referring to FIG. 6, an electrical schematic of a strain gauge 190 of apressure transducer such as the pressure transducer 100 in accordancewith one embodiment. The strain gauge 190 may be similar to the straingauge 110 and may include two active grids 191, 192 and two balancegrids 193, 194. However, unlike the strain gauge 110 but like the straingauge 180, the strain gauge 190 may include additional thermal resistors195, 196, 197, 198. Rather than the grids 191, 192, 193, 194 being theresistive element having a mismatched coefficient of thermal expansionrelative to the body, the additional thermal resistors 195, 196, 197,198 may be the resistive elements having mismatched coefficients ofthermal resistance relative to the body upon which they are attached. Inother embodiments, both the grids 191, 192, 193, 194 and the additionalthermal resistors 195, 196, 197, 198 may include mismatched coefficientsof thermal resistance relative to the body. The additional thermalresistors 195, 196, 197, 198 may be high impedance and/or resistancecircuit elements, particularly compared with the thermal resistors 185,186, 187, 188 connected in series described hereinabove with respect tothe strain gauge 180. The thermal resistors 195, 196, 197, 198 may eachbe connected in parallel to respective active and balance grids 191,192, 193, 194, as shown. In the embodiment shown, the thermal resistors195, 196 connected in parallel with the active grids 191, 192 may havethe same coefficient of thermal resistance as the thermal resistors 197,198 connected in parallel to the balance grids 193, 194 but may havedifferent resistances. In other embodiments, each of the thermalresistors 195, 196, 197, 198 may have the same resistance and differentcoefficients of thermal expansion. In other embodiments, each of thethermal resistors 195, 196, 197, 198 may have the same resistance anddifferent coefficients of thermal resistance. In other embodiments, eachof the thermal resistors 195, 196, 197, 198 may have the differentresistance and different coefficients of thermal resistance.

While the embodiments depicted in the figures include only in-linepressure transducers, other embodiments are contemplated utilizingmismatched resistive elements on a strain gauge relative to a body forother types of pressure transducers including, for example, diaphragmstyle pressure transducers.

Methods of detecting pressure are also contemplated. For example, amethod of detecting pressure may include providing a first pressuretransducer such as the first pressure transducer 100 having a body suchas the body 102 and a resistive element such as one or more of theresistive elements 122 attached to the body. The method may includemismatching a first coefficient of thermal expansion of the body to asecond coefficient of thermal expansion of the resistive element. Themethod may include detecting pressure of a fluid system with the firstpressure transducer. The method may include detecting pressure with thepressure transducer during an adiabatic thermal pulse. The method mayfurther include reducing settling time after the adiabatic thermal pulseby at least 50 percent relative to a second pressure transducer havingthe same properties as the first pressure transducer other than thesecond pressure transducer having well-matched coefficient of thermalexpansions. The second coefficient of thermal expansion may be greaterthan the first coefficient of thermal expansion. The method may stillfurther include outputting a positive output voltage during an adiabaticthermal pulse. The method may include compensating, with the mismatchedfirst and second coefficient thermal expansions, for an adiabaticthermal pulse.

Referring now to FIG. 7A, a top view of an in-line pressure transducer200 is shown in accordance with one embodiment. Similarly, FIG. 7B showsa side view of the pressure transducer 200 and FIG. 7C shows a crosssectional view of the pressure transducer 200 taken at arrows B-B. Thepressure transducer 200 includes a body 202, a fluidic inlet 204, afluidic outlet 206, and a fluidic cavity 208 extending between thefluidic inlet 204 and the fluidic outlet 206. The fluidic inlet 204 andthe fluidic outlet 206 may include inner threads (not shown) configuredto receive a connector, port, fitting or other coupling for connectingthe in-line pressure transducer 200 to a fluidic system, such as aliquid chromatography system. While the embodiment shown includes boththe fluidic inlet 204 and the fluidic outlet 206, other embodimentscontemplated include single ended transducers including a single fluidicinlet that acts as both a fluidic inlet and a fluidic outlet. In thisembodiment, the single fluidic inlet may be considered a fluidicinterface port.

The fluidic cavity 208 is enclosed by the body 202. A strain gauge 210is disposed on a surface 212 located on the outside of the body 202. Thesurface 212 may be a flat surface as shown. In other embodiments, thesurface 212 may include one or more curves thereon. The strain gauge 210includes a Wheatstone bridge having a first active grid 214 and a secondactive grid 216 located directly above the fluidic cavity 208 on thesurface 212, along with a first balance grid 218 disposed above thefluidic cavity 208 on the surface 212 and a second balance grid 220disposed below the fluidic cavity 208 on the surface 212. Theorientation and position of the active and balance grids 214, 216, 218,220 shown is exemplary and various other orientations are positions arecontemplated.

The fluidic cavity 208 may be considered a fluidic path or other fluidicbody configured to receive pressurized fluid. The strain gauge 210 maybe configured to detect the pressure in the fluidic cavity 208 or cavityby measuring the strain caused by the pressurized fluid on the body 202.The surface 212 may be a removed portion that is removed from the body202. In other embodiments, the surface 212 may be molded or otherwiseintegrated into the body 202. As shown in FIGS. 2B and 2C, the surface212 is located closer to the fluidic cavity 208 than the rest of theouter circumference of the body 202.

Within the fluidic cavity 208 is shown a filler body 230. The fillerbody 230 may extend a substantial length of the fluidic cavity 208, asshown in FIGS. 7A and 7B. The filler body 230 may extend almost theentire length of the fluidic cavity 208. In other embodiments, thefiller body 320 may be located only at the location located directlybelow the strain gauge 210 and/or surface 212.

The filler body 230 may be located within the fluidic cavity or fluidiccavity 208 and may be configured to reduce adiabatic thermal effects onthe body 202 of the pressure transducer 200. The filler body 230 mayreduce the volume within the fluidic cavity 208. As shown in FIG. 7C,the filler body 230 may further be configured to reduce the crosssectional area of the fluidic cavity or fluidic cavity 208 to a reducedcross sectional area 232. The reduced cross sectional area 232 may be agreater or larger area than the smallest cross sectional area at thefluidic inlet 204 and/or the fluidic outlet 206 after the fluidic inlet204 and fluidic outlet 206 has been connected in line to a fluidicsystem as described herein above. In other embodiments, the reducedcross sectional area 232 may be an equal cross sectional area to thesmallest cross sectional area at the fluidic inlet 204 and/or thefluidic outlet 206 after the fluidic inlet 204 and fluidic outlet 206has been connected in line to a fluidic system as described hereinabove. Whatever the embodiment, the reduced cross sectional area 232 maynot be a limiting dimension for reducing the volume of fluid flowthrough a fluidic system.

In one embodiment, the filler body 230 may include the same material asthe body 202 of the pressure transducer 200. In other embodiments, thefiller body 230 may be made of a material that is different than thematerial of the body 202. The filler body 230 and the body 202 may bemade of a metallic material such as, for example, zinc, stainless steel,titanium, Invar, or aluminum. In other embodiments, the body 202 may bea metallic material but the filler body 230 may be made of anon-metallic material such as a plastic, a composite or synthetic. Thefiller body 230 may be a separate component from the shape of thefluidic cavity 208 that is disposed within the fluidic cavity 208 duringfabrication of the pressure transducer 200. Disposing the filler body230 within the fluidic cavity 208 may include welding or otherwiseattaching the filler body into the fluidic cavity 208. In otherembodiments, the filler body 230 may simply be the integral shape of thefluidic cavity 208.

As shown in FIG. 7C, the filler body 230 may have a cylindrical shape.The cylindrical body or shape of the filler body 230 may have a diameterless than the diameter of the fluidic cavity 208. The filler body 230 isshown located at a location within the fluidic cavity or fluidic cavity208 that is distal to the strain gauge 210. In particular, the fillerbody 230 is located at a bottom of the fluidic cavity 208. Thus, thefiller body 230 may not contact a sensing region 231 of the innersurface of the fluidic cavity 208 that is located directly below thestrain gauge 210. The sensing region may include the upper half of theinner surface of the fluidic cavity 208. This may allow the fluid toflow closely to the web thickness so that the pressure transducer 200can more easily detect pressure within the fluidic cavity 208. Thefiller body 230 may be a solid cylinder as shown. A fluid path space 232is located above the filler body 230 between the filler body 230 and thecircumference of the fluidic cavity 208.

While the filler body 230 of FIGS. 7A-7C is a solid cylinder locatedwithin the fluidic cavity 208, other shaped filler bodies arecontemplated, as shown in FIGS. 8A-8F. While several shapes shown inFIGS. 8A-8F, the invention is not limited to these shapes.

FIG. 8A depicts a cross sectional view of an in-line pressure transducer240 at a midpoint along its length. The pressure transducer 240 includesa strain gauge 242, and a fluidic cavity or path 244. The pressuretransducer further includes a filler body 246 disposed within thefluidic cavity or path 244 configured to reduce the fluid volume foundwithin the fluidic cavity or path 244 at any given time. A first fluidpath space 248 may be located outside the filler body 246 and a secondfluid path space 249 may be located within the filler body 246. In thisembodiment, the filler body 246 may have a hollow cylindrical shape. Inother words, the filler body 246 may be a tubular body having a diameterless than the diameter of the fluidic cavity or path 244 and may belocated in the middle of the fluidic cavity or path 244. The filler body246 may be disposed within the fluidic cavity or path 244 in a loose orunattached manner. In other embodiments, the filler body 246 may beattached to the fluidic cavity or path 244 with an extending portion(not shown) that extends between the filler body 246 and fluidic cavity244 and holds the filler body 246 into the place shown.

FIG. 8B depicts a cross sectional view of an in-line pressure transducer250 at a midpoint along its length. The pressure transducer 250 includesa strain gauge 252, and a fluidic cavity or path 254. The pressuretransducer further includes a filler body 256 disposed within thefluidic cavity or path 254 configured to reduce the fluid volume foundwithin the fluidic cavity or path 254 at any given time. A fluid pathspace 258 may be located outside the filler body 246. In thisembodiment, the filler body 256 may have a solid cylindrical shapelarger than the filler body 230 described hereinabove. The filler body256 may be disposed within the fluidic cavity or path 256 at the bottomof the fluidic cavity or path 254 in a similar manner to the filler body230.

FIG. 8C depicts a cross sectional view of an in-line pressure transducer260 at a midpoint along its length. The pressure transducer 260 includesa strain gauge 262, and a fluidic cavity or path 264. The pressuretransducer further includes a filler body 266 disposed within thefluidic cavity or path 264 configured to reduce the fluid volume foundwithin the fluidic cavity or path 264 at any given time. A fluid pathspace 268 may be located above the filler body 266. The filler body 266may have a cylindrical shape with a flat removed portion disposed alongthe length of the cylinder at a circumferential location proximate thestrain gauge 262 when the filler body 266 is attached to the fluidiccavity 264. The filler body 266 may be attached to the fluidic cavity orpath 264. The filler body 266 may have a substantially similar outercircumference than the circumference of the fluidic cavity or path 264,with the exception of the removed portion.

FIG. 8D depicts a cross sectional view of an in-line pressure transducer270 at a midpoint along its length. The pressure transducer 270 includesa strain gauge 272, and a fluidic cavity or path 274. The pressuretransducer further includes a filler body 276 disposed within thefluidic cavity or path 274 configured to reduce the fluid volume foundwithin the fluidic cavity or path 274 at any given time. A first fluidpath space 278 may be located above the filler body 276 and a secondfluid path space 279 may be located below the filler body 276. In thisembodiment, the filler body 276 may be a flat bar extending across thecross sectional area of the fluidic cavity or path 274 having curvededges. The curved edges may correspond dimensionally to thecircumference of the fluidic cavity or path 274. The filler body 276 maybe attached to the fluidic cavity or path 274 at the curved edges.

FIG. 8E depicts a cross sectional view of an in-line pressure transducer280 at a midpoint along its length. The pressure transducer 280 includesa strain gauge 282, and a fluidic cavity or path 284. The pressuretransducer further includes a filler body 286 disposed within thefluidic cavity or path 284 configured to reduce the fluid volume foundwithin the fluidic cavity or path 284 at any given time. The filler body286 may be “X” shaped and may be attached to the fluidic cavity or path284 at the extensions of the X. A first fluid path space 285 may belocated above the filler body 286, a second fluid path space 287 may belocated to the right side of the filler body 286, a third fluid pathspace 288 may be located below the filler body 286 and a fourth fluidpath space 289 may be located to the left side of the filler body 286.

FIG. 8F depicts a cross sectional view of an in-line pressure transducer290 at a midpoint along its length. The pressure transducer 290 includesa strain gauge 292, and a fluidic cavity or path 294. The pressuretransducer further includes a filler body 296 disposed within thefluidic cavity or path 294 configured to reduce the fluid volume foundwithin the fluidic cavity or path 294 at any given time. The filler body296 may have a square shaped cross section with rounded or chamferedouter edges and may be attached to the fluidic cavity or path 294 at therounded outer edges. A first fluid path space 295 may be located abovethe filler body 296, a second fluid path space 297 may be located to theright side of the filler body 296, a third fluid path space 298 may belocated below the filler body 296 and a fourth fluid path space 299 maybe located to the left side of the filler body 296.

FIG. 9A depicts a top view of a diaphragm pressure transducer 300 inaccordance with one embodiment while FIG. 9B depicts a cutaway view ofthe pressure transducer of FIG. 8A taken at arrows C-C. The diaphragmpressure transducer 300 includes a body 302, a fluidic inlet 304, afluidic outlet 306, and a fluidic cavity 308 located between the fluidicinlet 304 and the fluidic outlet 306 and enclosed by the body 202. Whilethe embodiment shown includes both the fluidic inlet 304 and the fluidicoutlet 306, other embodiments contemplated include single endedtransducers including a single fluidic inlet that acts as both a fluidicinlet and a fluidic outlet. In this embodiment, the single fluidic inletmay be considered a fluidic interface port.

A strain gauge 310 is disposed on a diaphragm surface 312 located on theoutside of the body 302 of the diaphragm pressure transducer 300. Thestrain gauge 310 includes a Wheatstone bridge having grids as describedhereinabove. The strain gauge 310 may be configured to detect thepressure in the fluidic cavity 308 by measuring the strain caused by thepressurized fluid on the body 302 or diaphragm surface 312. Thediaphragm surface 312 may be a surface located above the fluidic cavity308.

Within the fluidic cavity 308 is shown a filler body 330. Like the filerbodies described hereinabove, the filler body 330 may be located withinthe fluidic cavity 308 and may be configured to reduce adiabatic thermaleffects on the body 302 of the pressure transducer 300. The filler body330 may reduce the volume within the fluidic cavity 308. As shown inFIG. 9B, the filler body 330 may further be configured to reduce thecross sectional area of the fluidic cavity 308. The reduced crosssectional area of the cavity 308 may be a greater or larger area thanthe smallest cross sectional area at the fluidic inlet 304 and/or thefluidic outlet 306. In other embodiments, the reduced cross sectionalarea may be an equal cross sectional area to the smallest crosssectional area at the fluidic inlet 304 and/or the fluidic outlet 306.Whatever the embodiment, the reduced cross sectional area may not be alimiting dimension for reducing the volume of fluid flow through afluidic system.

The filler body 330 and the body 302 of the diaphragm pressuretransducer 300 may be made of the same materials as those describedhereinabove with respect to the filler body 230 and the body 202 of thein-line pressure transducer 200. In creating or fabricating thediaphragm pressure transducer 300, a lower body portion 314 of the body302 and an upper body portion 316 of the body 302 may be joined, weldedor otherwise attached after the filler body 330 has been disposed,attached, or otherwise included into the cavity 308. In otherembodiments, the filler body 330 may simply be the integral shape of thefluidic cavity 308.

FIG. 10 depicts a graph 400 of the pressure transducer 200 is shownhaving the filler body 230 disposed or otherwise included in the fluidiccavity or path 208 compared to a pressure transducer having the sameproperties as the pressure transducer 200 except having no filler bodylocated with the fluidic cavity or path. The graph 400 plots pressureoutput of the strain gauges along the y-axis vs. settling time on thex-axis. In particular, the plot 412 shows the pressure transducer 200including the filler body 230, the strain gauge pressure output returnsto zero after only 0.15 seconds. In contrast, the plot 410 of thepressure transducer without the filler body returns to zero after onefull second. This long response time can be undesirable in industriesand applications where pressure must be detected immediately andadiabatic thermal events are common.

Further methods of fabricating a pressure transducer and/or detectingpressure are also contemplated. In one embodiment, a method includesproviding a pressure transducer such as one of the pressure transducers200, 300, having a fluidic inlet such as one of the fluid inlets 204,304, a fluidic outlet such as one of the fluid outs 206, 306, and afluidic cavity located between the fluidic inlet and the fluidic outletenclosed by the transducer body such as one of the fluidic cavities 208,308. The method may include attaching a strain gauge to the transducerbody such as one of the strain gauges 210, 310. The method may includeintegrating a filler body within the fluidic cavity, such as one of thefiller bodies 230, 246, 256, 266, 276, 286, 296, 330. The method mayinclude reducing a volume of the fluidic cavity with the filler body.Further, the method may include reducing adiabatic thermal effects onthe transducer body with the filler body relative to a second pressuretransducer having the same properties as the pressure transducer otherthan the second pressure transducer being fabricated without the fillerbody. The method may further include reducing the cavity cross sectionalarea to a reduced cross sectional area along a length of the cavity withthe filler body. The reduced cross sectional area may be greater than orequal to an inlet cross sectional area at the fluidic inlet. The methodmay include not contacting a sensing region of an inner surface of thefluidic cavity with the filler body, the sensing region, such as thesensing region 231, located directly below the strain gauge within thefiller cavity.

FIG. 11 depicts a schematic of a liquid chromatography system 500 inaccordance with one embodiment. The liquid chromatography system 500 mayinclude various features such as a solvent or mobile phase reservoir510, a pump, solvent manager or other solvent delivery system 520, asample container 530 with a sample injector or sample manager 540, aliquid chromatography column 550, a detector 560, a waste reservoir orsystem 570 and a control or computer system or other chromatogram 580.The liquid chromatography system 500 may be a fluidic system configuredto provide a mixed liquid comprising both the solvent 510 and the sample530 to the separation column 550 for separation and analysis by thedetector. The liquid chromatography system 500 may be a high performanceliquid chromatography system, a gas chromatography system, or the like.One or more of the pressure transducers described herein may be includedin the liquid chromatography system 500 to detect fluid pressure and/orprovide system control and/or system feedback. In one embodiment, one ormore of the pressure transducers described herein may be included in theliquid chromatography system 500 before, after and/or within the pump,solvent manager or solvent delivery system 520. Other locations in thesystem are also contemplated. Furthermore, other fluid systems besidesliquid chromatography systems may incorporate pressure transducersconsistent with embodiments described herein.

While the invention has been shown and described with reference tospecific embodiments, it should be understood by those skilled in theart that various changes in form and detail may be made therein withoutdeparting from the spirit and scope of the invention as recited in theaccompanying claims. For example, various embodiments of the micropipetare described as dispensing three or four aliquots, it should berecognized that in other embodiments the micropipet can be configured todeliver other numbers of aliquots from a single sample collection.

What is claimed is:
 1. A pressure transducer comprising: a body made ofa material having a first coefficient of thermal expansion; a fluidicinlet; a fluidic cavity enclosed by the body in fluidic communicationwith the fluidic inlet; and a strain gauge including a resistive elementin operable contact with the body, at least a portion of the resistiveelement made of a material having a second coefficient of thermalexpansion that is different from the first coefficient of thermalexpansion of the body, wherein the difference in the first coefficientof thermal expansion and the second coefficient of thermal expansion isconfigured to compensate for an adiabatic thermal pulse.
 2. The pressuretransducer of claim 1, wherein the resistive element further includes: afirst resistor in operable contact with the body; a second resistor inoperable contact with the body; a third resistor in operable contactwith the body; and a fourth resistor in operable contact with the body.3. The pressure transducer of claim 2, wherein the first, second, third,and fourth resistors are operably connected to form a Wheatstone bridge,and wherein the first and second resistors are active grids and whereinthe third and fourth resistors are balance grids.
 4. The pressuretransducer of claim 2, wherein the first, second, third, and fourthresistors are each made of the material having the second coefficient ofthermal expansion.
 5. The pressure transducer of claim 1, wherein adifference in the first coefficient of thermal expansion and the secondcoefficient of thermal expansion is configured to reduce settling timeafter an adiabatic thermal pulse relative to a second pressuretransducer having well-matched coefficient of thermal expansions.
 6. Thepressure transducer of claim 1, wherein the second coefficient ofthermal expansion is greater than the first coefficient of thermalexpansion.
 7. The pressure transducer of claim 1, wherein the differencein the first coefficient of thermal expansion and the second coefficientof thermal expansion is large enough that an output voltage disturbanceduring the adiabatic thermal pulse becomes positive.
 8. The pressuretransducer of claim 3, wherein the active grids are positioned proximatethe fluidic cavity and wherein the balance grids are positioned distalto the fluidic cavity relative to the active grids.
 9. The pressuretransducer of claim 3, wherein the balance grids are positioned in linewith the active grids and wherein the balance grids are orthogonallyoriented relative to the active grids.
 10. The pressure transducer ofclaim 2, wherein the first and second resistors are made of the materialhaving the second coefficient of thermal expansions and wherein thethird and the fourth resistors are made of the material having a thirdcoefficient of thermal expansion that is different than both the firstcoefficient of thermal expansion and the second coefficient of thermalexpansion.
 11. The pressure transducer of claim 2, wherein the firstresistor is directly connected in series to a first active grid of thestrain gauge, wherein the second resistor is directly connected inseries to a second active grid of the strain gauge, wherein the thirdresistor is directly connected in series to a first balance grid of thestrain gauge, and wherein the fourth resistor is directly connected inseries to a second balance grid of the strain gauge.
 12. The pressuretransducer of claim 2, wherein the first resistor is connected inparallel to a first active grid of the strain gauge, wherein the secondresistor is connected in parallel to a second active grid of the straingauge, wherein the third resistor is connected in parallel to a firstbalance grid of the strain gauge, and wherein the fourth resistor isconnected in parallel to a second balance grid of the strain gauge. 13.A method of detecting pressure comprising: providing a first pressuretransducer having a body and a resistive element attached to the body;mismatching a first coefficient of thermal expansion of the body to asecond coefficient of thermal expansion of the resistive element;detecting pressure of a fluid system with the first pressure transducer;and compensating, with the mismatched first and second coefficientthermal expansions, for an adiabatic thermal pulse.
 14. The method ofclaim 13, wherein the detecting pressure further comprises detectingpressure with the first pressure transducer during an adiabatic thermalpulse.
 15. The method of claim 14, further comprising reducing settlingtime after the adiabatic thermal pulse relative to a second pressuretransducer having well-matched coefficient of thermal expansions. 16.The method of claim 13, wherein the second coefficient of thermalexpansion is greater than the first coefficient of thermal expansion.17. The method of claim 14, further comprising outputting a positiveoutput voltage during an adiabatic thermal pulse.
 18. A liquidchromatography system comprising: a solvent delivery system; a sampledelivery system in fluidic communication with solvent delivery system; aliquid chromatography column located downstream from the solventdelivery system and the sample delivery system; a detector locateddownstream from the liquid chromatography column; and the pressuretransducer of claim 1.